Where to send a soil sample, when is the average last frost and is there hope for a frozen hibiscus?

DEAR JESSICA: I have potted outdoor hibiscus plants that I bought this past spring. Right now each plant looks like a small tree with dead green leaves. I wanted to know if they will come back next spring. If it’s not too late can I winterize them if necessary?

— Lisa Heymann,

Plainview

Mid-April is considered to be the "average" last frost date on Long Island. Photo Credit: Getty Images/iStockphoto / Mateusz K.

DEAR LISA: To answer your question — it’s too late. Hibiscus are tropical plants, which, by definition, means they won’t survive our winters. Your plant should have been brought indoors in September, before the threat of frost. Given the weather we’ve had this past month, it’s a safe assumption your plants are dead.

DEAR JESSICA: I read your reader’s concern about oak trees holding onto their leaves this late in the season. I also have oak trees on my property and have been a long-suffering homeowner who cleans leaves into January. You stated in your column that young trees hold the leaves as a protective mechanism. My trees are very mature and probably 60-plus years old. You also mentioned “infertile soil.” What does this mean and how can I find out if my soil is not in good condition?

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Have your soil tested to figure out what imbalances it might contain. Photo Credit: Getty Images/iStockphoto

Dear Craig: I’m glad you asked before going ahead and applying fertilizer around your oaks, as it’s important to confirm the soil is lacking the trees’ required nutrients first. Each plant has specific nutritional requirements, and what’s beneficial to one species may cause problems with another. For instance, too much nitrogen, a main component of many fertilizer products, could force an abundance of structurally weak growth, which could make your oaks susceptible to damage and disease.

Because neither of us knows the nutrient makeup of your soil, it’s important to have it tested before proceeding. I recommend you send a sample to Agro-One Soil Laboratory in upstate Ithaca, which will provide an analysis of your soil, as well as recommendations for correcting any imbalances. Visit nwsdy.li/soiltest or call 800-344-2697 to order a mailing box, obtain instructions for soil collection and submission, and get information about fees.

DEAR JESSICA: I read your article earlier this month about wrapping fig trees, and I am somewhat confused. You stated to unwrap it on a cloudy day in April, after the last frost. I was always told that the last frost meant May 15 on Long Island. That is when the tomatoes and hot peppers go in the ground. Was I misled by my nurseries all these years?

Hibiscus plants should be brought indoors in September, before the threat of frost. Photo Credit: Newsday / Thomas A. Ferrara

— Eric S. Rosenblum,

Levittown

DEAR ERIC: You weren’t misled, and it’s true that tomatoes, peppers and other summer vegetables should not be planted unprotected until at least the middle of May, which is when the danger of frost is considered to have passed. I should have specified that mid-April is when the “average” last frost date falls on Long Island, which is different. That date, specifically April 15, is applied to the rule for uncovering figs, because the earlier this is done, the greater the chances that the tree will mature all its fruits. It’s a balancing act, to be sure, because if uncovered too early, a spring frost could damage or kill the fruit.